Reinforced multi-body optical devices

ABSTRACT

A reinforced multi-body optical device that in one embodiment includes a multi-body optical device having a thickness that is less than or equal to about 1.0 millimeter and a supporting plate bonded without epoxy to the multi-body optical device. In an embodiment the supporting plate has a coefficient of thermal expansion (CTE) that is within about 0.5 parts per million of the CTE of the multi-body optical device.

CROSS-REFERENCES AND RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/941,284 filed Nov. 8, 2010, titled REINFORCED MULTI-BODY OPTICALDEVICES, which claims the benefit of Chinese Patent Application forInvention No. 201010112234.7, filed on Feb. 8, 2010, both of which arehereby incorporated by reference in their entireties.

BACKGROUND

An optical interleaver is a passive fiber-optic device that is used tointerleave two sets of dense wavelength-division multiplexing (DWDM)channels (odd and even channels) into a composite signal stream. Forexample, an optical interleaver can be configured to receive twomultiplexed signals with 100 GHz spacing and interleave them to create adenser DWDM signal with channels spaced 50 GHz apart. An opticalinterleaver can also function as a deinterleaver by reversing thedirection of the signal stream passing through the interleaver.

Optical interleavers have been widely used in DWDM systems and havebecome an important building block for optical networks withhigh-data-rate transmission. Optical interleavers are easier tomanufacture in some respects compared to other bandpass filteringtechnologies, such as thin-film filters and arrayed waveguided gratings.However, with the increased demand for smaller and smaller opticalinterleavers, attempts have been made to also reduce the size of theinternal components of the optical interleavers. However, as the sizesof the internal optical components are reduced, the process complexityof the fabrication of the internal components increases and the yield ofinternal components decreases.

BRIEF SUMMARY OF SOME EXAMPLE EMBODIMENTS

In general, example embodiments of the invention relate to reinforcedmulti-body optical devices. At least some example embodiments enhancethe strength of a multi-body optical device which enables themanufacture of a thinner multi-body optical device. The exampleembodiments disclosed herein also improve the long-term stability andreliability of these thinner multi-body optical device, even in harshapplication environments.

In one example embodiment, a method for fabricating a reinforcedmulti-body optical device includes various acts. First, a supportingplate is bonded, using pressure and heat, to a multi-body optical deviceto form a reinforced multi-body optical device. The supporting plate hasa coefficient of thermal expansion (CTE) that is within about 0.5 partsper million of the CTE of the multi-body optical device. Then, themulti-body optical device is ground to reduce the thickness of themulti-body optical device.

In another example embodiment, a method for fabricating a reinforcedmulti-body polarization beam splitter (PBS) includes various acts.First, a PBS coating is applied to either side of an interior plate.Next, two plates are bonded, using heat and pressure, to either side ofthe interior plate. Then, the bonded plates are diced at an angle thatis not orthogonal to the bonded plates. Next, the top and bottomportions of a diced section are removed to complete the formation of amulti-body PBS having a generally rectangular perimeter. Then, asupporting plate is bonded, using heat and pressure, to the multi-bodyPBS to form a reinforced multi-body PBS. The supporting plate has a CTEthat is within about 0.5 parts per million of the CTE of the multi-bodyPBS. Finally, the multi-body PBS is ground to reduce the thickness ofthe multi-body PBS.

In yet another example embodiment, a reinforced multi-body opticaldevice includes a multi-body optical device a supporting plate bondedwithout epoxy to the multi-body optical device. The multi-body opticaldevice has a thickness that is less than or equal to about 1.0millimeters. The supporting plate has a CTE that is within about 0.5parts per million of the CTE of the multi-body optical device.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential characteristics of the claimed subject matter, nor is itintended to be used as an aid in determining the scope of the claimedsubject matter.

Additional features will be set forth in the description which follows,and in part will be obvious from the description, or may be learned bythe practice of the teachings herein. Features of the invention may berealized and obtained by means of the instruments and combinationsparticularly pointed out in the appended claims. Features of the presentinvention will become more fully apparent from the following descriptionand appended claims, or may be learned by the practice of the inventionas set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

To further clarify certain aspects of the present invention, a moreparticular description of the invention will be rendered by reference toexample embodiments thereof which are disclosed in the appendeddrawings. It is appreciated that these drawings depict only exampleembodiments of the invention and are therefore not to be consideredlimiting of its scope. Aspects of the invention will be described andexplained with additional specificity and detail through the use of theaccompanying drawings in which:

FIG. 1A is a rear perspective view of an example optical deinterleaverhaving an example polarization beam displacer (PBD);

FIG. 1B is a perspective view of the example PBD of FIG. 1A;

FIG. 2 is a flowchart of an example method for fabricating the PBD ofFIGS. 1A and 1B;

FIGS. 3A-3L are schematic views of various example embodiments of theacts of the example method of FIG. 2;

FIG. 4 is a chart comparing various characteristics of a prior artdevice and the example PBD of FIGS. 1A and 1B that was fabricatedaccording to the example method of FIG. 2;

FIG. 5 is a side view of an example reinforced multi-body PBS array;

FIG. 6 is a flowchart of an example method for fabricating thereinforced multi-body PBS array of FIG. 5; and

FIGS. 7A-7J are schematic views of various example embodiments of theacts of the example method of FIG. 6.

DETAILED DESCRIPTION OF SOME EXAMPLE EMBODIMENTS

Example embodiments of the present invention relate to reinforcedoptical devices. At least some example embodiments enhance the strengthof an optical device which enables the manufacture of a thinnermulti-body optical device. The example embodiments disclosed herein alsoimprove the long-term stability and reliability of these thinnermulti-body optical device, even in harsh application environments.

Reference will now be made to the drawings to describe various aspectsof example embodiments of the invention. It is to be understood that thedrawings are diagrammatic and schematic representations of such exampleembodiments, and are not limiting of the present invention, nor are theynecessarily drawn to scale.

Reference is first made to FIG. 1A in which an example interleaver 100is disclosed. The example interleaver 100 is configured to interleave afirst optical signal with a second optical signal and configured todeinterleave the first optical signal from the second optical signal.For example, the interleaved optical signal can have 50 GHz channelspacing, while the two deinterleaved optical signals can each have 100GHz channel spacing.

As disclosed in FIG. 1A, the example interleaver 100 includes bases 102,a single-fiber collimator 104, a window cap 106, a first polarizationbeam displacing block 108, first and second filter cells 110 and 112interleaved with a first half-waveplate 114, and a second half-waveplate116. As disclosed in FIG. 1A, the example interleaver 100 also includesa third half-waveplate 118, a lateral shift prism 120, a roof prism 122,a second polarization beam displacing block 124, a window cap 126, and adual fiber collimator 128. As disclosed in FIG. 1A, the exampleinterleaver 100 further includes a combined polarization beam displacer250.

As disclosed in FIG. 1B, the polarization beam displacer (PBD) 250includes a polarization beam splitter (PBS) 252 and a retro-reflector254. Unlike typical configurations in which the PBS is separated fromthe retro-reflector by an air gap, the PBS 252 is bonded directly to theretro-reflector 254 without any air gap. This direct bonding can avoidthe need to coat the gap-facing sides of the PBS 252 and retro-reflector254 with an anti-reflective coating, thus decreasing the cost andcomplexity of the PBS 252 and retro-reflector 254. This direct bondingalso enables the retro-reflector 254 to reinforce the PBS 252, thusenabling the PBS 252 to be thinner than a stand-alone PBS, as discussedin greater detail below.

With reference now to FIG. 2, an example method 200 for fabricating thePBD 250 is disclosed. The acts of the example method 200 will now bediscussed in connections with FIG. 3A-3I.

With reference to FIGS. 2 and 3A, the method 200 begins with an act 202in which a coating, such as a PBS coating or other coating, is appliedto either side of an interior plate 302. The interior plate 302 can beformed from a variety of optically transmissive materials including, butnot limited to, silicon, plastics such as unfilled polyetherimide, fusedsilica, SF11 glass, and other glasses.

With reference to FIGS. 2 and 3B, the method 200 continues with an act204 in which two exterior plates 304 and 306 are bonded, using heat andpressure, to either side of the interior plate 302. The exterior plates304 and 306 can be formed from any of the materials listed above inconnection with the interior plate 302. In at least some exampleembodiments, the exterior plates 304 and 306 are formed from the samematerial as the interior plate 302. The exterior plates 304 and 306 canbe bonded to the interior plate 302 by first polishing the bondingsurfaces. Then, the exterior plates 304 and 306 can be pressed againsteither side of the interior plate 302. Finally, the plates 302, 304, and306 can be baked in an oven to complete the bonding process. Forexample, the plates 302, 304, and 306 can be baked in an oven at atemperature that is greater than or equal to 300 degrees Celsius. Thebaking at the act 204 can enable better molecular diffusion and adhesionbetween the bonded surfaces.

With reference to FIGS. 2, 3C, and 3D, the method 200 continues with anact 206 in which the bonded plates 302-306 are diced at an angle that isnot orthogonal to the bonded plates 302-306. For example, the bondedplates 302-306 may be diced along the dotted lines 308, resulting infour diced sections similar to the diced section 310 disclosed in FIG.3D.

With reference to FIGS. 2, 3D, and 3E, the method 200 continues with anact 208 in which a top portion 312 and a bottom portion 314 of a dicedsection 310 are removed to complete the formation of a multi-body PBS252 having a generally rectangular perimeter.

With reference to FIGS. 2, 3E, and 3F, the method 200 continues with anact 210 in which a supporting plate 318 is bonded, using heat andpressure, to the PBS 252 to form a reinforced PBS 320. For example, thePBS 252 can be bonded to the supporting plate 318 using a techniquesimilar to the technique discussed above in connection with the act 204.Also, the supporting plate can be formed from any of the materialslisted above in connection with the interior plate 302. For example, thesupporting plate 318 can be formed from the same material as the PBS252. Alternatively, in at least some example embodiments, the materialfrom which the supporting plate 318 is formed can have a coefficient ofthermal expansion (CTE) that is within about 0.5 parts per million ofthe CTE of the material from which the PBS 252 is formed.

With reference to FIGS. 2, 3G, and 3H, the method 200 continues with anact 212 in which the PBS 252 is ground to reduce the thickness of thePBS 252. As disclosed in FIG. 3G, this grinding can be accomplishedusing a grinder 322 that includes a mount 324 and a grinding plate 326.The supporting plate 318 of the reinforced PBS 320 can be mounted to themount 324 and the grinder 322 can then cause the mount 324 and thereinforced PBS 320 to rotate with respect to the grinding plate 326. Thefriction between the grinding plate 326 and the PBS 252 of thereinforced PBS 320 causes a portion of the PBS 252 to be ground away,resulting in a reduction of the thickness of the PBS 252, as disclosedin FIG. 3H. The thickness of the PBS 252 can be reduced to about 1.0millimeter or less. For example, the thickness of the PBS 252 can bereduced to about 0.3 millimeters or less. The grinding plate 326 can bea tar polishing plate, for example, although other types of grindingplates are possible and contemplated.

With reference to FIGS. 2, 3I, and 3J, the method 200 continues with anact 214 in which a first portion of the supporting plate 318 is groundat a first angle. As disclosed in FIGS. 3I and 3J, this grinding can beaccomplished using the grinder 322. As disclosed in FIG. 3I, the PBS 252of the reinforced PBS 320 can be mounted to the mount 324 at a firstangle to the grinding plate 326. The grinder 322 can then cause thegrinding plate 326 to rotate with respect to the mount 324 and thereinforced PBS 320. The friction between the grinding plate 326 and thesupporting plate 318 causes a corner of the supporting plate 318 to beground away, resulting in a first angled surface on the supporting plate318, as disclosed in FIG. 3J.

With reference to FIGS. 2, 3K, and 3L, the method 200 continues with anact 216 in which a second portion of the supporting plate 318 is groundat a second angle. As disclosed in FIG. 3K and 3J, this grinding can beaccomplished using the grinder 322. As disclosed in FIG. 3K, the PBS 252of the reinforced PBS 320 can be mounted to the mount 324 at a firstangle to the grinding plate 326. The grinder 322 can then cause thegrinding plate 326 to rotate with respect to the mount 324 and thereinforced PBS 320. The friction between the grinding plate 326 and thesupporting plate 318 causes a second corner of the supporting plate 318to be ground away, resulting in a second angled surface on thesupporting plate 318, as disclosed in FIG. 3L. Thus, the acts 214 and216 transform the supporting plate 318 into the retro-reflector 254 andtransform the reinforced PBS 320 into the PBD 250.

With reference to FIG. 4, a chart 400 compares a prior art PBD with thePBD 250. The prior art PBD includes a PBS and a retro-reflectorseparated by a 2 millimeter gap. As disclosed in the chart 400, thethickness of the PBS in both optical devices is about 1 millimeter andthe thickness of the retro-reflector in both optical device is about 3millimeters. However, the PBS and the retro-reflector of the prior artPBD is separated by a 2 millimeter gap, while the PBS 252 and theretro-reflector 254 of the PBD 250 are not separated by a gap and areinstead bonding directly to one another. Accordingly, the overallthickness of the prior art PBD is about 2 millimeters thicker than theoverall thickness of the PBD 250.

Further, the bond-facing surfaces of the PBS and the retro-reflector ofthe prior art PBD are also coated with an anti-reflective coating, whilethe PBS 252 and the retro-reflector 254 of the PBD 250 include no suchanti-reflective coating. Thus, the removal of the anti-reflectivecoating from the PBD 250 decreases the cost and complexity ofmanufacturing the PBD 250.

As disclosed in the chart 400, the yield of the PBD 250 is about 90percent, while the yield of the prior art PBD is only about 20 percent.In addition, the insertion loss of the PBD 250 is about half theinsertion loss of the prior art PBD, while the extinction ratio remainsabout equal between the two optical devices. Thus, the PBD 250 exhibitsa dramatic increase in the yield and a dramatic decrease in theinsertion loss over the prior art PBD. Further, the PBD 250 can bemanufactured with a decreased fabrication complexity and result exhibitless thermal deformation that the prior art PBD.

With reference now to FIG. 5, another type of optical device isdisclosed. In particular, FIG. 5 discloses a reinforced polarizationbeam splitter array (PBS array) 500. The reinforced PBS array 500includes a PBS array 502 and a supporting plate 504. The PBS array 502is bonded directly to the supporting plate 504. This direct bondingenables the supporting plate 504 to reinforce the PBS array 502, thusenabling the PBS array 502 to be thinner than a stand-alone PBS array,as discussed in greater detail below. Like the PBS 252 of FIGS. 1A and1B, the PBS array 502 is a multi-body optical device. However, insteadof being formed from only three components, the PBS array 502 is formedfrom five components.

With reference now to FIG. 6, an example method 600 for fabricating thereinforced PBS array 500 is disclosed. The acts of the example method600 will now be discussed in connections with FIG. 7A-7I.

With reference to FIGS. 6 and 7A, the method 600 begins with an act 602in which a coating, such as a PBS coating or other coating, is appliedto either side of first and second interior plates 702 a and 702 b. Theinterior plates 702 a and 702 b can be formed from a variety ofoptically transmissive materials including, but not limited to, any ofthe materials listed above in connection with the interior plate 302.

With reference to FIGS. 2 and 3B, the method 200 continues with an act604 in which the first and second interior plates 702 a and 702 b arebonded to either side of a third interior plates 702 c and two exteriorplates 704 and 706 are bonded to the interior plates 702 a and 702 b,using heat and pressure. The exterior plates 704 and 706 can be formedfrom any of the materials listed above in connection with the interiorplate 302. In at least some example embodiments, the exterior plates 704and 706 are formed from the same material as the interior plate 702. Theplates 704, 702 a, 702 c, 702 b, and 706 can be bonded to one another bypolishing the bonding surfaces, pressing the plates against one another,and baking the plates in an oven at a temperature that is greater thanor equal to 300 degrees Celsius, for example.

With reference to FIGS. 6, 7C, and 7D, the method 600 continues with anact 606 in which the bonded plates 704, 702 a, 702 c, 702 b, and 706 arediced at an angle that is not orthogonal to the bonded plates. Forexample, the bonded plates 704, 702 a, 702 c, 702 b, and 706 may bediced along the dotted lines 708, resulting in four diced sectionssimilar to the diced section 710 disclosed in FIG. 7D.

With reference to FIGS. 6, 7D, and 7E, the method 600 continues with anact 608 in which a top portion 712 and a bottom portion 714 of a dicedsection 710 are removed to complete the formation of a multi-body PBSarray 502 having a generally rectangular perimeter.

With reference to FIGS. 6, 7E, and 7F, the method 600 continues with anact 610 in which a supporting plate 504 is bonded, using heat andpressure, to the PBS array 502 to form the reinforced PBS array 500. Forexample, the PBS array 502 can be bonded to the supporting plate 504using a technique similar to the technique discussed above in connectionwith the act 604. Also, the supporting plate can be formed from any ofthe materials listed above in connection with the plates 704, 702 a, 702c, 702 b, and 706. For example the supporting plate 504 can be formedfrom the same material as the PBS array 502. Alternatively, in at leastsome example embodiments, the material from which the supporting plate504 is formed can have a CTE that is within about 0.5 parts per millionof the CTE of the material from which the PBS array 502 is formed.

With reference to FIGS. 6, 7G, and 7H, the method 600 continues with anact 612 in which the PBS array 502 is ground to reduce the thickness ofthe PBS array 502. As disclosed in FIG. 7G, this grinding can beaccomplished using the grinder 322, which is discussed above inconnection with FIGS. 3A-3L. The supporting plate 504 of the reinforcedPBS array 500 can be mounted to the mount 324 and the grinder 322 canthen cause the mount 324 and the reinforced PBS array 500 to rotate withrespect to the grinding plate 326. The friction between the grindingplate 326 and the PBS array 502 of the reinforced PBS array 500 causes aportion of the PBS array 502 to be ground away, resulting in a reductionof the thickness of the PBS array 502, as disclosed in FIG. 7H. Thethickness of the PBS array 502 can be reduced to about 1.0 millimeter orless. For example, the thickness of the PBS array 502 can be reduced toabout 0.3 millimeters or less.

With reference to FIGS. 6, 7I, and 7J, the method 600 continues with anact 614 in which the supporting plate 504 is ground to reduce thethickness of the supporting plate 504. As disclosed in FIG. 7I, thisgrinding can be accomplished using the grinder 322. The PBS array 502 ofthe reinforced PBS array 500 can be mounted to the mount 324 and thegrinder 322 can then cause the grinding plate 326 to rotate with respectto the mount 324 and the reinforced PBS array 500. The friction betweenthe grinding plate 326 and the supporting plate 504 of the reinforcedPBS array 500 causes a portion of the supporting plate 504 to be groundaway, resulting in a reduction of the thickness of the supporting plate504, as disclosed in FIG. 7J. The thickness of the supporting plate 504can be reduced to about 1.0 millimeter or less. For example, thethickness of the supporting plate 504 can be reduced to about 0.3millimeters or less.

Similar to the PBD 250, the reinforced multi-body PBS array 500 can bemanufactured with a higher yield than prior art PBS arrays. Further, thebonding of the supporting layer 504 to the multi-body PBS array 502reduces the thermal deformation of the multi-body PBS array 502. Themethod 600 also decreased the fabrication complexity, the thickness, andthe insertion loss of the reinforced multi-body PBS array 500.

The example embodiments disclosed herein may be embodied in otherspecific forms. The example embodiments disclosed herein are to beconsidered in all respects only as illustrative and not restrictive.

What is claimed is:
 1. A reinforced multi-body optical devicecomprising: a multi-body optical device having a thickness that is lessthan or equal to about 1.0 millimeters; and a supporting plate bondedwithout epoxy to the multi-body optical device, the supporting platehaving a CTE that is within about 0.5 parts per million of the CTE ofthe multi-body optical device.
 2. The reinforced multi-body opticaldevice as recited in claim 1, wherein the multi-body optical device is amulti-body polarization beam splitter (PBS).
 3. The reinforcedmulti-body optical device as recited in claim 1, wherein the supportingplate is a retro-reflector and the reinforced multi-body optical deviceis a reinforced polarization beam displacer (PBD).
 4. An opticalinterleaver comprising: first and second filter cells configured tofilter optical signals; the reinforced PBD as recited in claim 3optically coupled with the filter cells, the reinforced PBD configuredto reflect the optical signals; a single-fiber collimator opticallycoupled to the filter cells; and a dual-fiber collimator opticallycoupled to the filter cells.